With the initial clang-format definition and initial run with the config having been merged (#1127), the related issue (#901) was auto-closed, although its scope was greater than what the (huge) PR did. Therefore, I'm opening this follow-up issue for tracking the remaining parts for the actual integration.

Has this feature been discussed and generally agreed?

Yes, here: #901 (comment)
Some details still to be decided upon.

Describe the solution you'd like

• Make a final decision about the type of Github action (shamelessly copied from @passing's Automatic code linting for pull requests #901 (comment))
  1. Enforce style (auto-update PRs -- not sure if/how this is possible and feels like)
  2. Check style and block merge on invalid style (but I assume that admins can override in any case, needs to be checked).
  3. Check style, but don't block merge on invalid style.
• Implement the Github action
• Check if and what tools (Makefile?) or docs (CONTRIBUTING?) should be updated/extended for local clang checks